The present invention relates to an apparatus for use in fluidized solid systems and, more particularly, an apparatus which is particularly useful in the direct reduction of iron ores in a fluidized bed process.
A fluidized process of considerable importance relates to the direct reduction of iron ores. In typical fluidized processes for the reduction of iron ores, iron oxides are progressively reduced in a vertical vessel (reactor) having a single reduction stage or, more commonly, a series of reduction stages. In such processes, the ore to be reduced is fed into the top of the vessel and flows downwardly in counter current relationship to the flow of a fluidizing gas ascending in the vessel. The fluidizing gas comprises a hot reducing gas which consists generally of carbon monoxide, hydrogen and other known gas mixtures.
The fluidizing gases are delivered to the fluidizing bed for contact with the iron ore through a plurality of nozzles and provided in a horizontal wall disposed within the vessel. There is a considerable problem caused by the fouling and plugging of these nozzles particularly in fluidized processes for the direct reduction of iron ores. The fouling or plugging of the nozzles is associated with adherence of "fines" of metallic particles which adhere to the inner walls of the nozzles, build up on the inner walls and eventually plug the nozzles completely. It has been proposed in U.S. Pat. No. 3,910,769 to provide a baffle at the fluidizing gas inlet in combination with conical shaped nozzles so as to provide a preferential flow through the nozzles in a manner which would avoid adherence of the fines to the interior wall surface of the nozzles. While such a design has proven to be beneficial, the design has resulted in problems particularly with respect to the outer rings of nozzles. It has been found that the baffle plate causes a preferential deposition of the fines in the outer rings of the nozzles and, more particularly on a portion of the wall of the outer ring of the nozzles. This build-up results from a flow caused by the baffle plate which results in strong cross-flow at the nozzle inlets. Accordingly, the principal object of the present invention to provide a mechanism which eliminates the cross-flow at the nozzle inlets of the outer ring of nozzles thereby eliminating the excess build-up of fines on the outer ring of nozzles.